What large extinct animal once lived in the North, and lumbered across a land link between Siberia and Alaska? Most Yukoners will probably think first of a mammoth or a hairy mastodon wandering across the Beringian landscape, but someday dinosaurs of all shapes and sizes might also come to mind.

In the spring of 1999 dinosaur tracks were discovered in the Yukon for the first time. The previous summer a whole array of dinosaur tracks was found on Alaska's North Slope, and it is becoming clear that dinosaurs were not just an anomaly in this area millions of years ago.

The North was dinosaur land, as was Alberta and points much further south. And dinosaurs and other animals moved both ways across the Bering Land Bridge, just as they did during the Pleistocene Epoch.

"Some of my colleagues are referring to it as the Mesozoic Beringia," says Dr. Roland Gangloff, the curator of earth sciences at the University of Alaska Museum in Fairbanks.

Gangloff says that most dinosaur researchers now accept that dinosaurs moved between Asia and North America. The points of academic controversy have moved on to other issues.

"What we are arguing about now is how many dinosaurs there were, and in what directions they moved," he says.

Gangloff discovered both the Yukon tracks, found near Ross River, and those along Alaska's Colville River, discovered in 1998. There Gangloff and other researchers found both tracks and "trackways," meaning sets of prints, from five different types of dinosaurs. It was the first direct evidence that dinosaurs were numerous and diverse in the Arctic 90-110 million years ago.

"We have a diversity that tells us that they were not just freaks up here. Dinosaurs were widespread and abundant and diverse up here. That record is irrefutable," he says.

Gangloff describes the Yukon find as totally serendipitous. He and his assistant, Kevin May, were on their way back to Alaska from a dinosaur site in Grande Cache, Alberta, when they decided to take a side trip to the start of the Dempster Highway.

In the Ross River area they went to take a closer look at some promising rock formations, and soon found a range of footprints in the fine-grained sedimentary rock.

A set of prints appears to have been left by therapods, three-toed dinosaurs. Another print belongs to a hadrosaur or duck-billed dinosaur, which were among the last group of dinosaurs to appear before they all went extinct in the Cretaceous Period.

To date only one dinosaur bone has ever been found in the Yukon. Several decades ago a geologist working along the Bonnet Plume River found three small bones from a duck-billed dinosaur, or hadrosaur.

Remains of a hadrosaur were recently found in Antartica as well. "It is amazing that this terrestrial group extended all of the way from Antarctica to Alaska," he says.

Of course the world was a far different place in the days of the dinosaurs. The North was balmy, even temperate, and supported lush growths of vegetation. "This was a rich riverine deltaic environment. It could have supported great numbers of animals, including birds," says Gangloff.

Many of the Alaskan dinosaur discoveries, including an Edmontonia skull found in the Talkeetna Mountains and 140 million-year-old tracks on the Alaska Peninsula, were made during the oil exploration boom in the 1970s when geologists were scouring the state for hydrocarbon deposits.

Gangloff says there is no reason why similar finds shouldn't be made in the Canadian North, and he has put in a proposal to do research in the Mackenzie Mountains, following up on work done by another researcher who has since retired.

"I'm sure we are going to find much more in Canada than what has been found. I have no doubt that the high arctic was extensively populated. We are still in the early stages, and we have this huge area to cover. Even in Alaska we are just finding the tip of the iceberg," he says.

Gangloff says that finding dinosaur tracks is often a matter of just taking the time for a close look. When he first went to the Colville River area, he found the first track within an hour of getting out of the helicopter.

"Lots of geologists ran over that country for two decades and did not see them. There is no substitute for people spending time looking. Sometimes you cannot see them unless the lighting is just right," he says.

Gangloff plans to return to the Yukon next summer to work with John Storer, the Yukon's paleontologist. He says he would also love to look for more evidence of dinosaurs along the Bonnet Plume River.

He hopes to find more evidence to disprove a theory advanced in the 1980s by a paleobotanist who thinks that dinosaurs could have migrated between Alberta and Montana. While he thinks that this idea is wrong, he does not have enough evidence yet to prove it.

"It is too early for either of us to come out with a solid theory," he says.